These sweep tail rollers were designed to take the brunt of the impact while the sweep tail whips back and forth behind the cleaner as it moves along the surface of your pool. The rollers are loose enough to rotate as they hit the pool's surface ensuring that they don’t get stuck or caught up for any reason which could disrupt the cleaner during the cleaning process. This part is gray and is strategically placed along the sweep tail which means there is a total of 9 (only sold 3 to a pack). Made from a rubber-like compound These parts also prevent the hose from taking any unnecessary impact or damage. This also means that they will deteriorate over a length of time or use of the cleaner, needing to be replaced to restore its amazing cleaning capabilities.